If you are running macOS Monterey or later, you now have the ability to AirPlay your presentation directly from your iPad to the screen of your Mac. While this can be a benefit in some settings, it can also prevent you from sharing your iPad presentation using Zoom's built-in AirPlay.
If you want to present to Zoom you will need to turn off the ability to have your Mac act as an AirPlay Receiver. You can do this by going to System Preferences > Sharing and UNCHECK the box next to AirPlay Receiver.
If you later want to present to your Mac again, just go back into System Preferences > Sharing and CHECK the box next to AirPlay Receiver.
Please see our video tutorial about using TrialPad to present evidence over Zoom.